1. Field of the Invention
This invention relates to a bicycle brake, more particularly to a two-stage bicycle disk brake assembly with an anti-lock device, which can prevent instant braking of a bicycle wheel.
2. Description of the Related Art
Referring to FIG. 1, a conventional bicycle disk brake assembly is shown to include a caliper body 1 and two brake pads 103. The caliper body 1 is adapted to be mounted on a fork of a bicycle (not shown), and has a vertical passage 102 adapted to permit extension of a brake disk 2 of the wheel of the bicycle (not shown) therein, and a fluid reservoir 101 replete with a hydraulic fluid. When an external pressure is applied on the fluid in the fluid reservoir 101 by virtue of actuation of a brake lever of the bicycle (not shown), the brake pads 103 will move toward each other so as to clamp and lock the disk 2 therebetween, thereby braking the wheel (not shown). The aforesaid conventional brake assembly suffers from a drawback in that in a case where the speed of the bicycle is relatively high, when the bicycle is braked urgently, the action of the pads 103 on the disk 2 will result in skidding of the wheel on the road or overturning of the bicycle.
An object of this invention is to provide a two-stage bicycle disk brake assembly with an anti-lock device so as to prevent the occurrence of the above-stated drawback.
According to this invention, a bicycle disk brake assembly includes a pressure-reducing cylinder attached to a caliper body and formed with an inner chamber and outer chamber. Upon application of an external pressure to a hydraulic fluid, which is filled within a fluid reservoir in the caliper body, the fluid flows from the reservoir to the outer chamber. When the fluid pressure in the outer chamber reaches a first value, an inner check valve is operated so as to permit flow of the fluid from the outer chamber to the inner chamber. Thereafter, when the fluid pressure in the inner chamber reaches a second value and when the external pressure is released, a resilient member biases the fluid in the inner chamber to activate an outer check valve, thereby permitting flow of the fluid from the inner chamber to the outer chamber and subsequently to the reservoir.